Thermoplastic molding materials

ABSTRACT

A thermoplastic molding composition, comprising 
     (A) from 20 to 99% by weight of at least one graft copolymer, 
     (B) from 1 to 80% by weight of a copolymer of at least one alpha-olefin and from at least one polar comonomer, with the proviso that the monomers used are not vinyl acetate or any vinylaromatic monomer, and 
     (C) from 0 to 80% by weight of a thermoplastic polymer, prepared by polymerizing a monomer mixture, comprising 
     (c1) from 50 to 100% by weight of at least one vinylaromatic monomer and/or of a C 1 -C 8 -alkyl (meth)acrylate, and 
     (c2) from 0 to 50% by weight of at least one monofunctional comonomer, and 
     (D) from 0.1 to 20% by weight of a substantially uncrosslinked, low-molecular-weight polyalkyl acrylate.

The invention relates to thermoplastic molding compositions based on ASA(acrylonitrile-styrene-acrylate) and comprising acrylate copolymers andhaving improved flowability and improved extrusion properties. Theinvention further relates to a process for preparing these thermoplasticmolding compositions and to their use, and also to films, moldings andcoatings produced therefrom and having reduced gloss, and to the use ofthese.

There is a wide variety of application sectors for thermoplastic moldingcompositions, and there is therefore a variety of known moldingcompositions with differing mixes for different application sectors.

EP-A 0 526 813 describes polymer blends for flexible films. These aremade from a graft copolymer of vinyl monomers as graft shell on anacrylate rubber as graft base, a partially crosslinked copolymer rubberbased on acrylate, an uncrosslinked polymer based on styrene compoundsand/or on acrylic compounds and an ethylene-vinyl acetate copolymer. Theplastic material which can be obtained, in which no PVC is present, issuitable for producing leather-like films. However, these mixtures tendto discolor undesirably during processing and have a disadvantageousrelationship between tensile strength and elongation at break. Films ofthis type also exhibit relatively severe fogging when processed bymethods similar to those conventionally used.

DE-A 31 49 358 relates to thermoplastic molding compositions obtainablefrom a graft copolymer with a core made from a crosslinked alkylacrylate and, if desired, from comonomers and with a shell obtainable bypolymerizing a vinylaromatic monomer with an ethylenically unsaturatedmonomer, and with a copolymer obtainable by polymerizing a vinylaromaticmonomer with an ethylenically unsaturated monomer. Films produced fromthese thermoplastic molding compositions have the disadvantage ofexcessively low elongation at break together with excessively highhardness. Molding compositions of this type are moreover unsuitable forsoft coextrusion compositions.

Plastic films with reduced-gloss surface and leather-like appearance areused, for example, for interior trim in motor vehicles. The plasticusually used nowadays is PVC, mixed with a variety of vinyl polymers andplasticizers. These films are not fully aging-resistant at hightemperatures, and they comprise volatile constituents and naturallycontain halogen (see DE-A 42 11 415).

The use of acrylate copolymers (component (D)) in thermoplastic moldingcompositions based on poly-olefins, PVC, SAN or ABS is known.

BE-A 782 372 (Derwent abstract) relates to thermo-plastic compositionswhich are composed of a vinyl halide copolymer and from 0.1 to 4.0% byweight of a liquid acrylic homo- or copolymer. The acrylic copolymerserves as lubricant and improves the processibility of the vinyl halidecopolymer.

CA-A 923645 relates to thermoplastic molding compositions which comprisea liquid alkyl acrylate homo- or copolymer to lower their viscosity.

Thermoplastic molding compositions which may be used are vinylaromatichomo- or copolymers, in particular ABS (acrylonitrile-butadiene-styrene)polymers, polymers or copolymers of vinyl chloride, or poly-carbonates.The hardness, impact strength and heat distortion temperature (HDT) ofthe thermoplastic molding compositions are not substantially affected byadding the liquid acrylate homopolymers or copolymers.

There is no hitherto known use of acrylate copolymers in moldingcompositions which are composed predominately of ASA graft rubber(acrylonitrile-styrene-acrylate) with SAN (styrene-acrylonitrile)copolymers and with an olefin polymer.

It is an object of the present invention, therefore, to providethermoplastic molding compositions which may be used either as films orelse as soft, reduced-gloss surface coatings for hard, brittle orimpact-modified thermoplastics. These molding compositions are appliedas coatings, for example by coextrusion, and for this have to have goodflowability. However, in order not to be damaged during furtherprocessing, coating compositions of this type still have to have a highlevel of mechanical strength and heat resistance, in particular adequatefor use in the automotive interior sector. A further object was toprovide a process for preparing these thermoplastic moldingcompositions, and also the use of the molding compositions of theinvention for producing moldings or films, or as coextrusioncompositions. The films should have a balanced ratio of ultimate tensilestrength, elongation at break, tear propagation resistance, hardness andcolorfastness during processing, and also have reduced surface gloss andreduced susceptibility to electrostatic charging. In particular, tearpropagation resistances to DIN 53515 of at least 35 N/mm should beachieved by the films, and the films should be aging-resistant andhalogen-free with a leather-like appearance and comprise a lower levelof volatile constituents than corresponding films of the prior art.Other objects are to provide films and moldings made from the moldingcompositions of the invention which have good and balanced mechanicalproperties, and the use of these.

We have found that this object is achieved, as are the other objectsdescribed, by way of thermoplastic molding compositions, essentiallycomprising

(A) from 20 to 99% by weight of at least one graft copolymer,essentially obtainable from

(a1) from 30 to 90% by weight of a core, obtainable by polymerizing amonomer mixture, essentially consisting of

(a11) from 80 to 99.99% by weight of at least one C₁-C₁₀-alkyl acrylate,

(a12) from 0.01 to 20% by weight of at least one copolymerizable,polyfunctional, cross-linking monomer, and

(a13) from 0 to 40% by weight, based on the total weight of components(a11) and (a12), of at least one other copolymerizable,mono-ethylenically unsaturated monomer, and

(a2) from 10 to 70% by weight of a graft shell, obtainable bypolymerizing a monomer mixture in the presence of the core (a1), andessentially consisting of

(a21) from 50 to 100% by weight of at least one styrene compound of theformula (I)

where R¹ and R², independently of one another, are hydrogen orC₁-C₈-alkyl and/or of a C₁-C₈-alkyl (meth)acrylate, and

(a22) from 0 to 50% by weight of at least one monofunctional comonomer,and

(B) from 1 to 80% by weight of a copolymer obtainable from at least onealpha-olefin and from at least one polar comonomer, with the provisothat the monomers used are not vinyl acetate or any vinylaromaticmonomer, and

(C) from 0 to 80% by weight of a thermoplastic polymer, obtainable bypolymerizing a monomer mixture, essentially consisting of

(c1) from 50 to 100% by weight of at least one vinylaromatic monomerand/or of a C₁-C₈-alkyl (meth)acrylate, and

(c2) from 0 to 50% by weight of at least one monofunctional comonomer,and

(D) from 0.1 to 20% by weight of a substantially uncrosslinked,low-molecular-weight polyalkyl acrylate with a molar mass of from 300 to25 000 g/mol, where the overall total of components A to D is 100% byweight.

These molding compositions have excellent flowability and very goodextrusion properties. They can be processed to give films or moldingswith a soft, matt surface, at, consistent product quality. The moldingcompositions have a high level of mechanical strength and heatresistance. They are readily coextrudable. The molding compositions ofthe invention are particularly suitable for injection molding. Films andmoldings made from these molding compositions have reduced surface glossand reduced susceptibility to electrostatic charging. They are suitablefor interior trim in motor vehicles, in the construction of houses, forthe sanitary sector and for the furniture sector.

The molding compositions of the invention achieve the abovementionedcombination of properties. The fundamental properties for film use areachieved here by mixing components (A) to (C), and the overall propertyprofile for application in coextrusion is achieved by mixing components(A) to (D). Component (D) brings about not only the improvement inflowability but also a lowering of Shore hardness, without significantimpairment of mechanical properties.

The amount of component (A) present in the molding compositions of theinvention, based on the total of components (A) to (D), is from 20 to99% by weight, preferably from 30 to 98% by weight and particularlypreferably from 50 to 95% by weight. This component is a particulategraft copolymer built up from an elastomeric graft core (a1) (“softcomponent”) and, grafted onto this, a shell (a2) (“hard component”).

The amount of the graft core (a1), based on component (A), is from 30 to90% by weight, preferably from 35 to 80% by weight and particularlypreferably from 40 to 75% by weight.

The graft core (a1) is obtained by polymerizing a monomer mixture madefrom, based on (a1),

(a11) from 80 to 99.99% by weight, preferably from 90 to 99.85% byweight and particularly preferably from 97 to 99% by weight, of at leastone C₁-C₁₀-alkyl acrylate,

(a12) from 0.01 to 20% by weight, preferably from 0.2 to 10% by weightand particularly preferably from 0.5 to 5% by weight, of at least onecrosslinking monomer, and

(a13) from 0 to 40% by weight, preferably from 0 to 10% by weight, basedon the total weight of components (a11) and (a12), of at least one othercopolymerizable, monoethylenically unsaturated monomer.

Particularly suitable C₁-C₁₀-alkyl acrylates (component (a11)) aremethyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate,n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octylacrylate, 2-ethyl-hexyl acrylate, n-nonyl acrylate and n-decyl acrylate,and also mixtures of these, particularly preferably ethyl acrylate,2-ethylhexyl acrylate, n-butyl acrylate or mixtures of these, and veryparticularly preferably n-butyl acrylate.

The copolymerizable, polyfunctional crosslinking monomers (a12) used aregenerally those which contain two, three or four, preferably two,copolymerizable double bonds which are not 1,3-conjugated in. Examplesof monomers of this type suitable for crosslinking are ethylene glycoldiacrylate, ethylene glycol dimethacrylate, butanediol diacrylate,butanediol dimethacrylate, hexanediol diacrylate, hexanedioldimethacrylate, divinylbenzene, diallyl maleate, diallyl fumarate,diallyl phthalate, triallyl cyanurate, triallyl isocyanurate,tricyclodecenyl acrylate, dihydrodicyclopentadienyl acrylate, triallylphosphate, allyl acrylate, allyl methacrylate and dicyclopentadienylacrylate (DCPA) (cf. DE-C-12 60 135).

Other examples which may be mentioned of copolymerizable,monoethylenically unsaturated monomers (component (a13)) are butadiene,isoprene;

vinylaromatic monomers, such as styrene or styrene derivatives of theformula I;

methacrylonitrile, acrylonitrile;

acrylic acid, methacrylic acid, dicarboxylic acids, such as maleic acidand fumaric acid, and also anhydrides of these, such as maleicanhydride;

nitrogen-functional monomers, such as dimethyl-aminomethyl acrylate,dimethylaminoethyl acrylate, vinylimidazole, vinylpyrrolidine,vinylcaprolactam, vinylcarbazole, vinylaniline, acrylamide;

C₁-C₄-alkyl methacrylates, such as methyl methacrylate, ethylmethacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, sec-butyl methacrylate andhydroxyethyl acrylate;

aromatic or araliphatic (meth)acrylates, such as phenyl acrylate, phenylmethacrylate, 2-phenylethyl acrylate, 2-phenylethyl methacrylate, benzylmethacrylate, benzyl acrylate, 2-phenoxyethyl methacrylate and2-phenoxy-ethyl acrylate;

unsaturated ethers, such as vinyl methyl ether,

and also mixtures of these monomers.

The amount of the graft shell (a2) present, based on component (A), isfrom 70 to 10% by weight, preferably from 65 to 20% by weight,particularly preferably from 60 to 25% by weight, and it is obtainableby polymerizing a monomer mixture in the presence of the core (a1).

The graft shell (a2) is obtained by polymerizing a monomer mixture madefrom, based on (a2),

(a21) from 50 to 100% by weight, preferably from 55 to 95% by weight,particularly preferably from 60 to 90% by weight, of at least onestyrene compound of the formula (I)

where R¹ and R², independently of one another, are hydrogen orC₁-C₈-alkyl and/or of a C₁-C₈-alkyl (meth)acrylate, and

(a22) from 0 to 50% by weight, preferably from 45 to 5% by weight,particularly preferably from 40 to 10% by weight, of at least onemono-functional comonomer.

The styrene compound used of the formula (I) (component (a21)) ispreferably styrene, α-methylstyrene or ring-C₁-C₈-alkyl-alkylatedstyrenes, such as p-methylstyrene or tert-butylstyrene, particularlypreferably styrene or α-methylstyrene.

According to the invention, the C₁-C₈-alkyl (meth)acrylates used aremethyl methacrylate (MMA), ethyl methacrylate, n- or isopropylmethacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butylmethacrylate, tert-butyl methacrylate, pentyl methacrylate, hexylmethacrylate, heptyl methacrylate, octyl methacrylate or 2-ethylhexylmethacrylate, particularly preferably methyl methacrylate, or mixturesof these monomers, methyl acrylate (MA), ethyl acrylate, propylacrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate,tert-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate,octyl acrylate or 2-ethylhexyl acrylate, particularly preferably n-butylacrylate, or else a mixture of these monomers with one another or withthe methacrylates and/or styrene compounds of the formula I, where theamount of the acrylates in the graft shell is preferably subordinate.

Possible monofunctional comonomers (component (a22)) are monomersselected from the group consisting of methacrylonitrile, acrylonitrileand mixtures of these, N—C₁-C₈-alkyl-, N—C₅-C₈-cycloalkyl- andN—C₆-C₁₀-aryl-substituted maleimides, such as N-methyl-, N-phenyl-,N-dimethylphenyl- and N-cyclohexylmaleimide, and maleic anhydride.Acrylonitrile is preferred.

It is preferable for the graft shell (a2) to have been built up fromstyrene or from a mixture comprising from 65 to 85% by weight ofstyrene, the remainder being acrylonitrile.

In a preferred embodiment the graft shell (a2) is built up using amixture of styrene (S) and acrylonitrile (AN) (molar ratio S/AN usuallyfrom 4.5:1 to 0.5:1, preferably from 2.2:1 to 0.65:1), styrene on itsown, a mixture of acrylonitrile and methyl methacrylate (MMA) or MMA onits own.

Component (A) is prepared by methods known per se, for example asdescribed in DE-A 31 49 358.

For this, the core (a1) is first prepared by polymerizing theacrylate(s) (a11) and the poly-functional crosslinking monomers (a12),if desired together with the other comonomers (a13), in usually aqueousemulsion, in a manner known per se at from 20 to 100° C., preferablyfrom 50 to 800° C. Use may be made of the usual emulsifiers, such asalkali metal alkyl- or alkylarylsulfonates, alkyl sulfates, fattyalcohol sulfonates, salts of higher fatty acids having from 10 to 30carbon atoms, sulfosuccinates, such as Aerosol® OT (Cyanamid), ethersulfonates, such as Disponil® FES61 (Henkel) or resin soaps (Dresinate).Preference is given to the use of the sodium or potassiumalkylsulfonates, or of salts of fatty acids having from 10 to 18 carbonatoms.

The usual amounts of emulsifiers may be used. Advantageous amounts ofemulsifiers are from 0.3 to 5% by weight, in particular from 1 to 2% byweight, based on the monomers used in preparing the core (a1).

The dispersion is preferably prepared using sufficient water to give thefinished dispersion a solids content of from 20 to 60% by weight.

Preferred polymerization initiators are free-radical generators, forexample peroxides, preferably peroxo-sulfates, such as potassiumperoxodisulfate, and azo compounds, such as azodiisobutyronitrile.However, it is also possible to use redox systems, in particular thosebased on hydroperoxides, such as cumene hydroperoxide. Concomitant usemay also be made of from 0 to 3% by weight of molecular weightregulators, such as ethylhexyl thioglycolate, tert-dodecyl mercaptan,terpinols or dimeric α-methylstyrene.

The amount of the initiators generally depends on the desired molecularweight and is usually from 0.1 to 1% by weight, based on the monomersused in preparing the core (a1).

To maintain a constant pH, preferably from 6 to 9, buffer substances maybe used as polymerization auxiliaries, for example Na₂HPO₄/NaH₂PO₄ orsodium hydrogencarbonate. The usual amounts of the buffer substances areused, and further details in this connection are therefore unnecessary.

The precise polymerization conditions, in particular the type, method ofaddition and amount of the emulsifier, are generally determinedindividually within the ranges given above in such a way as to give theresultant latex of the crosslinked acrylate polymer (a1) a d₅₀ of from60 to 1000 nm, preferably from 80 to 800 nm, particularly preferablyfrom 100 to 600 nm. The particle size distribution of the latex hereshould preferably be narrow.

The graft core (a1) may particularly preferably also be prepared bypolymerizing the monomers (a11) to (a13) in the presence of afine-particle latex made from elastomeric or hard polymers (seed-latexpoly-merization). The seed latex used may, for example, have been madefrom crosslinked poly-n-butyl acrylate or from polystyrene.

It is also in principle possible to prepare the graft core (a1) by aprocess other than emulsion poly-merization, e.g. by bulk or solutionpolymerization, and then to emulsify the resultant polymers.Microsuspension polymerization is also suitable, preferably usingoil-soluble initiators, such as lauroyl peroxide or tert-butylperpivalate. The processes for this are known.

In a preferred embodiment the core (a1) has a glass transitiontemperature below 0° C.

The graft-rubber particles (A) usually have a particle size (d₅₀) offrom 60 to 1 500 nm, preferably from 100 to 1 200 nm.

In a particularly preferred embodiment, graft-rubber particles (A) witha particle size (d₅₀) of from 150 to 700 nm are used in order to givethe molding composition high toughness.

In another preferred embodiment, a mixture of graft-rubber particles (A)of different sizes which has a bimodal particle size distribution isused. In a particularly preferred mixture of this type, from 0.5 to99.5% by weight of the mixture has a particle size, as given by theaverage diameter (d₅₀), of from 200 to 1000 nm, and from 0.5 to 99.5% byweight of the mixture has a particle size, as given by the averagediameter (d₅₀), of from 60 to 190 nm.

The chemical structure of the two graft polymers is preferably the same,although the shell of the coarse-particle graft polymer may inparticular also have a two-stage structure.

The graft shell (component (a2)) is generally likewise prepared by knownpolymerization processes, such as emulsion, bulk, solution or suspensionpolymerization, preferably in aqueous emulsion in the presence of anaqueous emulsion of the core (a1) (see DE-A 12 60 135, DE-A 31 49 358and DE-C 11 64 080). In a preferred embodiment, the graftcopolymerization is carried out in a system which is the same as thatused for the polymerization of the core (a1) with addition, if required,of further emulsifier and initiator. These do not have to be the same asthe emulsifiers or initiators used for preparing the core (a1). Theemulsifier, the initiator and the polymerization auxiliaries may each becharged on their own or in a mixture to the dispersion of the core (a1).Any of the possible combinations of, on the one hand, charging andfeeding and, on the other hand, initiator, emulsifier and polymerizationauxiliaries may be used. Preferred embodiments are those known to theskilled worker. The monomer or, respectively, monomer mixture to begrafted on may be added to the reaction mixture all at once, batchwisein two or more stages or else continuously during the polymerization.

The amount of component (B) present in the molding compositions of theinvention, based on the total of components (A) to (D), is from 80 to 1%by weight, preferably from 60 to 3% by weight, particularly preferablyfrom 50 to 4% by weight.

Alpha-olefins used to prepare component (B) may be C₂-C₈-alpha-olefins,such as ethene, propene, 1-butene, 1-pentene, 1-hexene, 1-heptene or1-octene, or mixtures of these, preferably ethene or propene.

Examples of polar comonomers, which according to the invention shouldnot include vinyl acetate or vinylaromatic monomers, are:

alpha- or beta-unsaturated C₃-C₈ carboxylic acids and the availableanhydrides of these, for example acrylic acid, methacrylic acid, maleicacid, maleic anhydride, fumaric acid, itaconic acid, and glycerideesters thereof and also esters with C₁-C₈-alkyl alcohols whose alkylradicals may have monosubstitution by phenyl groups or by naphthylgroups, unsubstituted or mono- or di-C₁-C₄-alkyl-substituted phenol ornaphthol, methyl methacrylate, ethyl methacrylate, n-butyl acrylate,isobutyl acrylate, pentyl acrylate, hexyl acrylate, 2-ethylhexylacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, phenylacrylate, phenylethyl methacrylate, phenylethyl acrylate, benzylmethacrylate, benzyl acrylate, phenylpropyl methacrylate, phenylpropylacrylate, phenylbutyl methacrylate, phenylbutyl acrylate, 4-methylphenylacrylate, naphthyl acrylate, phenoxyethyl methacrylate and phenoxyethylacrylate;

methacrylonitrile, acrylonitrile;

carbon monoxide.

In a preferred embodiment, copolymers used as component (B) can beprepared from (I) 40 to 75% by weight of ethylene, from 5 to 20% byweight of carbon monoxide and 20 to 40% by weight of n-butyl acrylate,for example the commercially available ELVALOY® HP-4051 (DuPont), orpreferably from (II) 50 to 98.9% by weight of ethylene, 1 to 45% byweight of n-butyl acrylate and 0.1 to 20% by weight of (meth)acrylicacid and/or maleic anhydride or from (III) 96 to 67% by weight ofethylene, 1 to 20% by weight of n-butyl acrylate, 3 to 10% by weight of(meth)acrylic acid and 0 to 3% by weight of maleic anhydride.

The copolymers (B) are prepared in a manner known per se (see U.S. Pat.No. 2,897,183 and U.S. Pat. No. 5,057,593). They are usually prepared byfree-radical polymerization. The initiators usually used are peroxides,such as lauroyl peroxide, tert-butyl peracetate, tert-butylperoxy-pivalate, di-tert-butyl peroxide, di(sec-butyl)peroxydicarbonate, tert-butyl peroctanoate and tert-butylperisononanoate, preferably tert-butyl peroxy-pivalate and tert-butylperisononanoate. Initiators containing azo groups, such asazobisisobutyronitrile, are also suitable.

The choice of the suitable initiator usually depends on thepolymerization temperature to be selected, which is generally from 100to 300° C., preferably from 130 to 280° C. The pressure during thepolymerization is usually selected within the range from 100 to 400 MPa,preferably from 150 to 250 MPa. The amount of initiator is generallychosen within the range from 1 to 50 mol, preferably from 2 to 20 mol,for each 10⁶ mol of polar copolymer used.

The polymerization is generally carried out in a continuously operatingtubular reactor. A reactor of this type is described, for example, inU.S. Pat. No. 2,897,183. The reaction time is generally from 30 to 1min, preferably from 5 to 2 min. The use of a solvent has hitherto beenfound to be optional.

The proportion of component (C) in the molding compositions is from 0 to80% by weight, preferably from 5 to 60% by weight, particularlypreferably from 10 to 30% by weight, based on the total of components(A) to (D) . This polymer is obtainable by polymerizing a monomermixture essentially consisting of

(c1) from 50 to 100% by weight, preferably from 60 to 95% by weight,particularly preferably from 65 to 80% by weight, of at least onevinylaromatic monomer and/or of a C₁-C₈-alkyl (meth)acrylate, and

(c2) from 0 to 50% by weight, preferably from 0 to 40% by weight,particularly preferably from 5 to 35% by weight, of at least onemonofunctional comonomer,

based in each case on component (C).

The vinylaromatic monomer (component (c1)) used comprises styrene, thesubstituted styrenes of the formula (I) mentioned above as component(a21) or the C₁-C₈-alkyl (meth)acrylates mentioned under component(a21), preferably methyl methacrylate. Preference is given to the use ofstyrene, α-methylstyrene and p-methylstyrene.

Monomers which may be used as monofunctional comonomers (component (c2))are those mentioned above as component (a22). The component (c2) usedmay also, if desired, be a mixture of the C₁-C₈-alkyl (meth)acrylatesmentioned under component (a21) and the monomers mentioned undercomponent (a21). Preference is given to mono-ethylenically unsaturatednitrile compounds, in particular acrylonitrile, methacrylonitrile andmixtures of these. Acrylonitrile is particularly preferred.

In a preferred embodiment, use is made of a mixture of styrene (S) andacrylonitrile (AN), S and α-methyl-styrene, if desired mixed with methylmethacrylate or with maleimides, or of methyl methacrylate, if desiredwith methyl acrylate. Particular preference is given to SAN polymerswhose principal components are styrene and acrylonitrile.

The polymers of component (C) are generally known. In some cases theyare also commercially available, or can be prepared by known methods(see Kunststoff-Handbuch, Vieweg-Daumiller, Vol. V (Polystyrol)[(Polystyrene)], Carl-Hanser-Verlag, Munich 1969, page 118 et seq.). Thepolymerization is generally carried out by a free-radical route inemulsion, or in suspension, solution or bulk, the latter two methodsbeing preferred. The polymers (C) generally have viscosity numbers (VN)(measured to DIN 53 726 in a 0.5% strength solution in dimethylformamideat 25° C.) of from 40 to 160 ml/g, corresponding to average molar massesM_(w) of from 40 000 to 2 000 000.

The proportion of component (D) in the molding compositions, based onthe total of components (A) to (D), is from 0.1 to 20% by weight,preferably from 0.2 to 15% by weight and in particular from 0.3 to 10%by weight. Component (D) is a substantially uncrosslinked,low-molecular-weight polyalkyl acrylate with a molar mass of from 300 to25 000 g/mol, preferably from 500 to 20 000 g/mol, particularlypreferably from 1 000 to 15 000 g/mol.

The molar masses given are average molar masses and are given asnumber-average M_(n).

The polyalkyl acrylates used are generally polyalkyl acrylates havingfrom 2 to 10 carbon atoms in the alkyl radical. Preference is given topolyethyl, polybutyl, polyhexyl and polyethylhexyl acrylate. Use ofpolybutyl acrylate is particularly preferred.

Very particular preference is given to use, as component (D), of asubstantially uncrosslinked poly-butyl acrylate with a molar mass ofabout 1 000 g/mol.

For the purposes of the present invention, substantially uncrosslinkedimplies a gel content of generally not more than 49%, preferably notmore than 40%. Particular preference is given to products whose gelcontents are so low that they are completely soluble.

Component (D) is prepared by known polymerization processes, preferablyby way of free-radical polymerization in solution, the solvent beingremoved prior to or after the mixing of components (A) to (D) and, whereappropriate, other components.

Products of this type, for example those based on n-butyl acrylate, arecommercially available, for example as the Acronal group of productsfrom BASF.

Besides components (A), (B), (C) and (D), the thermo-plastic moldingcompositions may also comprise additives, such as lubricants,mold-release agents, pigments, dyes, flame retardants, antioxidants,light stabilizers, fibrous or pulverulent fillers, fibrous orpulverulent reinforcing materials, and antistats, the amounts beingthose usual for these materials.

The invention further provides a process for preparing thermoplasticmolding compositions in a manner known per se, by mixing, in a mixingapparatus,

(A) from 20 to 99% by weight of at least one graft copolymer,essentially obtainable from

(a1) from 30 to 90% by weight of a core, obtainable by polymerizing amonomer mixture, essentially consisting of

(a11) from 80 to 99.99% by weight of at least one C₁-C₁₀-alkyl acrylate,

(a12) from 0.01 to 20% by weight of at least one copolymerizable,polyfunctional, crosslinking monomer, and

(a13) from 0 to 40% by weight, based on the total weight of components(a11) and (a12), of at least one other copoly-merizable,monoethylenically unsaturated monomer, and

(a2) from 70 to 10% by weight of a graft shell, obtainable bypolymerizing a monomer mixture in the presence of the core (a1), andessentially consisting of

(a21) from 50 to 100% by weight of at least one styrene compound of theformula (I)

where R¹ and R², independently of one another, are hydrogen orC₁-C₈-alkyl and/or of a C₁-C₈-alkyl (meth)acrylate, and

(a22) from 0 to 50% by weight of at least one monofunctional comonomer,

and

(B) from 1 to 80% by weight of a copolymer obtainable from at least oneα-olefin and from at least one polar comonomer, with the proviso thatthe monomers used are not vinyl acetate or any vinylaromatic monomer,

and

(C) from 0 to 80% by weight of a thermoplastic polymer, obtainable bypolymerizing a monomer mixture, essentially consisting of

(c1) from 50 to 100% by weight of at least one vinylaromatic monomerand/or of a C₁-C₈-alkyl (meth)acrylate, and

(c2) from 0 to 50% by weight of at least one monofunctional comonomer,

and

(D) from 0.1 to 20% by weight of a substantially uncrosslinked,low-molecular-weight polyalkyl acrylate with a molar mass of from 300 to25 000 g/mol,

where the overall total of components A to D is 100% by weight.

and, where appropriate, conventional additives.

The molding compositions of the invention may be prepared by mixingprocesses known per se, for example by melting in a mixing apparatus,e.g. an extruder, Banbury mixer or kneader, or on a roll mill orcalender at from 150 to 300° C. It is also possible, however, for thecomponents to be mixed “cold” without melting and for the mixture,composed of powder or pellets, not to be melted and homogenized until itis processed.

The molding compositions of the invention may be used to producemoldings, films or fibers. The invention therefore also provides thecorresponding moldings, films and fibers.

The invention also provides the use of the molding compositions of theinvention for coating sheet-like structures to give sheet-likestructures with a reduced-gloss surface by way of coextrusion.

The molding compositions of the invention may be used to producemoldings of any type, in particular films. The films may be produced byextrusion, rolling, calendering or other processes known to the skilledworker, usually at from 150 to 280° C. Preference is given to theproduction of films from the molding compositions via extrusion. Themolding compositions of the invention are molded here by heating and/orfriction, on their own or with concomitant use of plasticizing or otheradditives, to give a processible film. Examples of equipment suitablefor this purpose are extruders with slot dies. The films usually have athickness of from 0.05 to 2 mm. An example of a process used to makefinished products from films of this type is thermoforming at, forexample, from 120 to 170° C.

In a preferred embodiment, coatings or leather-like films are producedby mixing

(A) from 20 to 99% by weight of at least one graft copolymer,essentially obtainable from

(a1) from 30 to 90% by weight of a core, obtainable by polymerizing amonomer mixture, essentially consisting of

(a11) from 80 to 99.99% by weight of n-butyl acrylate, and

(a12) from 0.01 to 20% by weight of tricyclo-decenyl acrylate, and

(a2) from 10 to 70% by weight of a graft shell, obtainable bypolymerizing a monomer mixture in the presence of the core (a1), andessentially consisting of

(a21) from 60 to 90% by weight of styrene and

(a22) from 10 to 40% by weight of acrylo-nitrile, and

(B) from 1 to 80% by weight of a copolymer, prepared from

from 67 to 96% by weight of ethylene,

from 1 to 20% by weight of n-butyl acrylate,

from 3 to 10% by weight of (meth)acrylic acid, and

from 0 to 3% by weight of maleic anhydride, and

(C) from 0 to 80% by weight of a copolymer, prepared by continuoussolution polymerization of

(c1) from 65 to 85% by weight of styrene and

(c2) from 15 to 35% by weight of acrylonitrile, and

(D) from 0.1 to 20% by weight of a substantially uncrosslinkedlow-molecular-weight polyalkyl acrylate with a molar mass of from 300 to25 000 g/mol,

where the overall total of components A to D is 100% by weight,

and then calendering or extruding to give films.

The molding compositions of the invention may also be used forcoextrusion together with other polymers, giving coextruded moldings orcoextruded films. Examples of these other polymers are ABS(acrylonitrile-butadiene-styrene polymers), PBT (polybutyleneterephthalate), ASA (acrylonitrile-styrene-acrylate), PVC (polyvinylchloride), SAN (styrene-acrylonitrile copolymers), MABS (methylmethacrylate-acrylonitrile-butadiene-styrene polymers), polymethylmethacrylate, polycarbonate and others.

The coated sheet-like structures and the films with leather-likeappearance have a wide variety of applications, in particular in theautomotive industry for the construction of automotive interiors, fordecorative purposes, as a leather substitute in producing suitcases orbags and in the furniture industry as a coating material for thelamination of furniture surfaces.

Coextruded sheets may be further processed by thermoforming, for examplefor use in the sanitary sector, in containers (e.g. hard-shellsuitcases) or in the decorative or furniture sector.

The present invention therefore also provides the use of coatedsheet-like structures or of films with a leather-like appearance for theinternal fitting-out of houses, utility vehicles, aircraft, ships ortrains, in the furniture industry and in the sanitary sector.

The molding compositions may also be extruded or coextruded to givepipes, tubes or profiles.

The thermoplastic molding compositions of the invention are preferablyhalogen-free. They are very substantially free from constituents whichescape by evaporation or bleed out, and exhibit practically nodisadvantageous changes during processing, for example discoloration. Inparticular, even without the concomitant use of appropriate stabilizersor other additives, they have excellent heat-aging resistance and lightresistance, and also good mechanical properties.

In particular, the molding compositions of the invention feature goodflowability, especially when processed by extrusion. The good extrusionproperties of the molding compositions bring about very consistentproduct quality of the films.

EXAMPLES

The following constituents were prepared (all percentages given are byweight):

Preparation of a Component A

Particulate graft copolymer made from crosslinked poly-n-butyl acrylate(core) and styrene-acrylonitrile copolymer (shell)

A mixture made from 98 g of n-butyl acrylate and 2 g ofdihydrodicyclopentadienyl acrylate and also, separately, a solution of 1g of Na C₁₂-C₁₈-paraffin-sulfonate in 50 g of water were added at 60° C.over the course of 4 hours to a mixture made from 3 g of a polybutylacrylate seed latex, 100 g of water and 0.2 g of potassium persulfate.The polymerization was then continued for a further 3 hours. The averageparticle diameter d₅₀ of the resultant latex was 430 nm with a narrowparticle size distribution (Q=0.1).

150 g of this latex were mixed with 60 g of water, 0.03 g of potassiumpersulfate and 0.05 g of lauroyl peroxide, and then firstly 20 g ofstyrene were grafted at 65° C. onto the latex particles over the courseof 3 hours, followed by a mixture of 15 g of styrene and 5 g ofacrylonitrile over the course of a further 4 hours. The polymer was thenprecipitated by a calcium chloride solution at 95° C., separated off,washed with water and dried in a stream of warm air. The degree ofgrafting in the polymer was 35% and the average diameter d₅₀ of theparticles was 510 nm.

The makeup of the graft copolymer was as follows (rounded values):

65% by weight of a graft core made from polybutyl acrylate, crosslinked,

15% by weight of an inner graft made from styrene polymer, and

20% by weight of an outer graft made from styrene-acrylonitrilecopolymer with an S/AN weight ratio of 3:1.

The seed polymer used at the outset was prepared by the process of EP-B6503 (column 12, line 55 to column 13, line 22) by polymerizing n-butylacrylate and tricyclodecenyl acrylate in aqueous emulsion, and had asolids content of 40%.

The average particle size mentioned in describing component (A) is theweight-average of the particle sizes.

The average diameter is the d₅₀, denoting that 50% by weight of all theparticles have a smaller diameter, and 50% by weight a larger diameter,than the diameter corresponding to the d₅₀. To characterize the breadthof the particle size distribution, the d₁₀ and d₉₀ values are frequentlygiven in addition to the d₅₀. 10% by weight of all the particles aresmaller, and 90% by weight are larger, than the d₁₀ diameter. In asimilar way, 90% by weight of all of the particles have a smallerdiameter, and 10% by weight a larger diameter, than the diametercorresponding to the d₉₀. The quotient Q=(d₉₀−d₁₀)/d₅₀ is a measure ofthe breadth of the particle size distribution. A smaller Q indicates anarrower distribution.

Component B

A copolymer was prepared from 67-96% by weight of ethylene, 1-20% byweight of butyl acrylate, 3-10% by weight of acrylic acid and 0-3% byweight of maleic anhydride.

Component B is a commercially available product and is available as theLupolen® group of products from BASF, for example.

Preparation of a Component C

Copolymer Made From Styrene and Acrylonitrile

A copolymer made from 65% by weight of styrene and 35% by weight ofacrylonitrile (component C) was prepared by continuous solutionpolymerization, as described in Kunststoff-Handbuch, ed. R. Vieweg undG. Daumiller, Vol. V “Polystyrol” [“Polystyrene”], Carl-Hanser-VerlagMunich 1969, pp. 122-124. The viscosity number VN (determined inaccordance with DIN 53 726 at 25° C., 0.5% by weight indimethylformamide) was 60 ml/g.

Component D

Component (D) is prepared by known polymerization processes, preferablyby way of free-radical poly-merization in solution, the solvent beingremoved prior to or after mixing of components (A) to (D) and, whereappropriate, other components.

Products of this type, for example those based on n-butyl acrylate, arecommercially available, for example as the Acronal® group of productsfrom BASF.

Molding Compositions Prepared and Their Properties

Components A to D were intimately mixed, with melting, at 240° C. and250 rpm in a Werner+Pfleiderer ZSK30 twin-screw extruder, discharged andpelletized. The pellets were extruded in a Rheocord 90 single-screw 3:1Haake extruder at 220° C. and from 160 to 220 rpm to give a film ofthickness 0.6 mm, using a slot die with 0.5 mm gap.

The following properties were determined for the films:

Tensile strength: the tensile test was undertaken to DIN 53 504 onstrips stamped out from the film.

Elongation at break: elongation at ultimate tensile stress wasdetermined in the tensile test to DIN 53 504 and given in % of theinitial dimension of the strip.

Tear propagation resistance: a tear propagation test was undertaken toDIN 43 515 on strips stamped out from the material.

Shore hardness: the Shore hardness was determined to DIN 43 505 usingtest apparatus D.

Heat resistance: determined to DIN 53 406 as Vicat value using testmethod A.

The flowability of the molding compositions was determined on pellets,by measuring the melt volume rate (MVR) at 220° C. or 200° C. with aload of 10 kp or 21.6 kp. The amount discharged from a standard die in10 min is given in ml.

The mixes for the films produced and the results of the tests are givenin Table 1.

TABLE 1 Example/ 1 (com- 2 (com- Component parison) parison) 3 4 5 6A/pts. by wt. 70 70 70 70 70 70 B/pts. by wt. 15 20 15 15 20 20 C(SAN)/pts. 15 10 15 15 10 10 by wt. D1/pts. by wt. — — 3 5 3 5 MVR 25.138.7 39.1 44.6 61 82 220/21.6/ml/ 10 min MVR 10.5 15.9 15.9 18.8 25 31200/21.6/ml/ 10 min MVR 0.46 0.66 0.67 1.0 0.6 2.5 220/10/ml/ 10 minShore D/° 41 39 42 41 37 35 Vicat A/° C. 82 70 78 72.2 64 59 Tensile 1613 13 14 13 11 strength N/mm² Elongation 144 188 124 141 170 167 atbreak/% Tear 50.3 39 42 42 37 33 propagation resistance/N/ mm²

Component (D) has an effect on flowability, hardness and mechanicalproperties, depending on the initial mix used.

We claim:
 1. A thermoplastic molding composition, comprising (A) from 20to 99% by weight of at least one graft copolymer, prepared from (a1)from 30 to 90% by weight of a core, obtainable by polymerizing a monomermixture, consisting essentially of (a11) from 80 to 99.99% by weight ofat least one C₁-C₁₀-alkyl acrylate, (a12) from 0.01 to 20% by weight ofat least one copolymerizable, poly-functional, crosslinking monomer, and(a13) from 0 to 40% by weight, based on the total weight of components(a11) and (a12), of at least one other copolymerizable,monoethylenically unsaturated monomer, and (a2) from 10 to 70% by weightof a graft shell, obtainable by polymerizing a monomer mixture in thepresence of the core (a1), and consisting essentially of (a21) from 50to 100% by weight of at least one styrene compound of the formula (I)

where R¹ and R², independently of one another, are hydrogen orC₁-C₈-alkyl and/or of a C₁-C₈-alkyl (meth)acrylate, and (a22) from 0 to50% by weight of at least one monofunctional comonomer, and (B) from 1to 80% by weight of a copolymer prepared from at least one alpha-olefinand from at least one polar comonomer, with the proviso that themonomers used are not vinyl acetate or any vinylaromatic monomer, and(C) from 0 to 80% by weight of a thermoplastic polymer, obtainable bypolymerizing a monomer mixture, consisting essentially of (c1) from 50to 100% by weight of at least one vinylaromatic monomer and/or of aC₁-C₈-alkyl (meth)acrylate, and (c2) from 0 to 50% by weight of at leastone monofunctional comonomer, and (D) from 0.1 to 20% by weight of asubstantially uncrosslinked polyalkyl acrylate with a number averagemolar mass M_(n) of from 300 to 25 000 g/mol, where the overall total ofcomponents A to D is 100% by weight.
 2. A thermoplastic moldingcomposition as claimed in claim 1, wherein the particle size of thegraft copolymers (A) as determined by the average diameter (d₅₀) is from60 to 1 500 nm.
 3. A thermoplastic molding composition as claimed inclaim 2, wherein the particle size as determined by the average diameter(d₅₀) is from 150 to 700 nm.
 4. A thermoplastic molding composition asclaimed in claim 1, wherein the particle size distribution of component(A) is bimodal.
 5. A thermoplastic molding composition as claimed inclaim 4, wherein the component (A) used comprises a mixture of from 0.5to 99.5% by weight of a graft copolymer (A) whose particle size asdetermined by the average diameter (d₅₀) is from 200 to 1000 nm and from99.5 to 0.5% by weight of a graft copolymer (A) whose particle size asgiven by the average diameter (d₅₀) is from 60 to 190 nm.
 6. Athermoplastic molding composition as claimed in claim 1, wherein theglass transition temperature of the core (a1) is selected to be below 0°C.
 7. A process for preparing thermoplastic molding compositions asclaimed in claim 1 which comprises mixing the components of claim 1 and,optionally, conventional additives in a mixing apparatus.
 8. A processfor producing films comprising the step of extruding, rolling orcalandering the thermoplastic molding compositions as claimed inclaim
 1. 9. A process for producing sheets with a reduced-gloss surfacecomprising coextruding the thermoplastic molding compositions ofclaim
 1. 10. A film obtainable by the process as claimed in claim
 8. 11.A film with appearance of leather, produced by mixing (A) from 20 to 99%by weight of at least one graft copolymer, essentially obtainable from(a1) from 30 to 90% by weight of a core, obtainable by polymerizing amonomer mixture, consisting essentially of (a11) from 80 to 99.99% byweight of n-butyl acrylate, and (a12) from 0.01 to 20% by weight oftricyclodecenyl acrylate, and (a2) from 10 to 70% by weight of a graftshell, obtainable by polymerizing a monomer mixture in the presence ofthe core (a1), and essentially consisting of (a21) from 60 to 90% byweight of styrene and (a22) from 40 to 10% by weight of acrylonitrile,and (B) from 1 to 80% by weight of a copolymer, prepared from from 67 to96% by weight of ethylene, from 1 to 20% by weight of n-butyl acrylate,from 3 to 10% by weight of (meth)acrylic acid, and from 0 to 3% byweight of maleic anhydride, and (C) from 0 to 80% by weight of acopolymer, prepared by continuous solution polymerization of (c1) from65 to 85% by weight of styrene and (c2) from 15 to 35% by weight ofacrylonitrile, and (D) from 0.1 to 20% by weight of an essentiallyuncrosslinked polyalkyl acrylate with a number average molar mass M_(n)of from 300 to 25 000 g/mol, where the overall total of components A toD is 100% by weight, and then calendering or extruding to give a film.